Lanning was ruled out of the Ashes and the home summer after undergoing surgery on her injured shoulder. Alex Blackwell, 34, remains the vice-captain of the side.
Haynes has played three Tests, 36 ODIs and 27 T20Is. She returned to the Australian squad earlier this year following a three-and-a-half-year absence, and was also given the nod to stand in for the injured Lanning in two ICC Women's World Cup matches in July ahead of the experienced Blackwell. Interestingly, the two matches she led in were also the only ones Haynes played at the World Cup.
"To be named captain of your country, particularly in such a big series like the Ashes, is a huge honour," ESPNcricinfo quoted Haynes as saying.
"It's going to be a really exciting series, I think the multi-format points system in particular doesn't favour either team, so to win the Ashes you genuinely have to be the best team across all three formats," the 30-year-old added.
The multi-format Ashes begins on October 22 and includes three ODIs followed by a day-night Test and three T20Is.
Haynes will be Australia's 19th Test captain when the first ever women's day-night Test gets underway at North Sydney Oval on November 9.
"To be the first team male or female to play in a day-night Ashes Test match is going to be awesome," said Haynes. "To have that opportunity is really exciting, you can only ever be part of history once."
Haynes's hiatus from international cricket ended in February this year when she was a called up to the ODI squad against New Zealand as an injury cover for Blackwell. (ANI)